In recent years, wheels of motor vehicles have been aligned using a computer-aided, three-dimensional (3D) machine vision alignment system. In such a system, one or more cameras view targets attached to the wheels of the vehicle, and a computer in the alignment system analyzes the images of the targets to determine wheel position and to determine alignment of the vehicle wheels from the wheel position data. The computer typically guides an operator in properly adjusting the wheels to accomplish precise alignment, based on calculations obtained from processing of the image data. A wheel alignment system or aligner of this type is sometimes called a “3D aligner.” An example of a vehicle wheel aligner using such image processing is the Visualiner 3D, commercially available from John Bean Company, Conway, Ark., a unit of Snap-on Tools Company.
Alignment systems of the type outlined above utilize at least one “image sensor,” which is a light sensitive sensor capable of sensing a two-dimensional array image. An image sensor typically is a component of an imaging module, which communicates with the host computer. In addition to the sensor array, circuits in the module include timing and control circuitry for the sensor and possibly analog processing circuitry, e.g. amplification, filtering and/or gain control circuitry. The module circuitry usually includes an analog to digital (A/D) converter, to convert the sensor pixel measurement signals to digital data values, and data communication circuitry for communications with the external host computer. The module may also contain a processor and memory to provide additional control and pre-processing of the sensor array data. Attention is directed to US Patent Application Publication No. 2004/0128844 to Robb et al., assigned to the assignee of the present subject matter and incorporated herein by reference.
Often, the imaging module includes other system components. For example, the module may include a strobe or the like for target illumination as well as indicators or display devices to provide operator guidance. A positioning system, for controlling the position of the imaging module relative to the viewable target, may be contained within the imaging module or be external to the imaging module. Such a positioning system enables adjustment of the height and/or one or more angles or directions of orientation of the image sensor relative to the subject.
In early generation image based wheel alignment systems, the various elements of the imaging module were implemented with functionally discreet components on large and expensive circuit boards. As more powerful integrated circuits were developed some of these functions have been combined on a single chip. FIG. 7 is a block diagram illustrating the elements on the integrated circuit of the prior art incorporating an image sensor, sensor control logic and some associated signal processing circuitry.
As shown, the integrated circuit 14 includes an image sensor, in the form of a complementary metal oxide semiconductor (CMOS) detector array 12. The integrated circuit 14 also includes image sensor logic 16 serving as the sensor controller. The image sensor logic 16 communicates with the detector array 12 to control the output from pixels of the array 12 and to thereby control the operation of the array. The controller 16 also directs communications via the input/output 22 for the integrated circuit 14, including communication of signals for control, data and addresses, as the circuit 14 communicates with an external host computer system across an interface bus 26. The prior integrated circuit 14 also includes analog to digital (A/D) converter 30 and signal conditioning circuitry 28.
Additionally, a processor 34 on the integrated circuit 14 can be programmed, so that the integrated circuit 14 becomes an application specific integrated circuit (ASIC). An internal bus 18 on the integrated circuit 14 provides control, address and data signaling between the elements of the integrated circuit. Depending on the ASIC, the processor 34 can include a digital signal processor, a micro-processor, and/or a micro-controller processor. The processor 34 on the integrated circuit 14 may be implemented to perform the desired alignment computations previously executed in the host computer. Hence, one such ASIC design can calculate orientation and position, for a machine vision alignment system, whereas another ASIC design might calculate angles and positions in a wheel-mounted alignment system.
Many of the other wheel alignment system functions, however, including other functions typically performed in the imaging module, are still implemented independently and are not integrated into the circuit with the image sensor. Hence, there is still room for further improvement.